Castiel the Avenger 2: The Dark World
by RandomHamster33
Summary: Reading 'Castiel the Avenger' before this is advised, but not required. Summary: A visit from an old "friend" warns Castiel of a dark future ahead; Asgard is under attack.
1. Aether

Hello everyone! This is a sequel to *Castiel the Avenger*! There's no way that this would have come about if not for the oh so amazing Bornrider2! They came up with the idea and asked me write it, so this is a collab operation. As such, some parts, or even *chapters*, may be written by me or them. (Not sure yet as we just started [kinda not anymore {I've been procrastinating big one}] this, but we'll sort it all out). If I could put a link to Bornrider2's profile, I would.

* * *

Takes place in Thor: The Dark World.

_Long before the birth of light, there was darkness. And from the darkness, came the Dark Elves. Millennia ago, most ruthless of their kind, Malekith, sought to transform our universe back into one of eternal night. Such evil was possible through the power of the Aether, an ancient force of infinite destruction._

Algrim, a Dark Elf, approached his leader: Malekith. He spoke in elvish. "Malekith, the Asgardians attack."

_The noble armies of Asgard, led by my father King Bor, waged a mighty war against these creatures. But Asgard was not alone in defeating the Dark Elves. Stories speak of a great warrior, more powerful than anyone they'd ever seen, even the King himself. With the help of the warrior, the Asgard ripped the weapon from Malekith's grasp, and without it, the Dark Elves fell. With the battle all but lost, Malekith sacrificed his own people, in a desperate attempt to lay waste to Asgard's army._

"Through their sacrifice we will survive," Malekith hissed to Algrim. "It will not be in vain." The two board a spaceship, leaving the army to their fate.

_Malekith was vanquished and the Aether was no more. Or so we were led to believe . . ._

A soldier piped up from the bloody and wasted battlefield. "Sire, the Aether. Shall we destroy it?"

"If only we could," King Bor said grimly, "but its power is too great. Bury it deep, somewhere no one will ever find it."

* * *

"I'll take my leave," Castiel said, and was gone, leaving Dean growling and yelling:

"Freakin' angels!"

Castiel stood outside the restaurant; a small cafe. Reapers crowded the streets and sidewalks around the area. It seemed like Lucifer was here; all the signs pointed to that. He glanced around, searching for any demons. There were none he could see, so he moved forward. His trench coat swayed behind him, rhythmically following his motions.

The reapers numbly watched the angel as he weaved through their midst. Castiel knew he had to keep his guard up, or else he might end up in the wrong place. He didn't want to be ambushed or attacked. Glancing around, Castiel prepared to enter the cafe, when he heard the faintest sound of wings behind him; only a trained observer could have noticed the disguised angel.

"Heya Cassie!" Castiel turned from his target to see Gabriel waving for him to follow.

"Gabriel, why are you here?" Castiel asked. He walked over to the archangel. His eyes scanned the reapers, keeping a close eye on things.

Gabriel chuckled. "You can't sense it? It's the convergence, Castiel!" He threw his arms out, as if in humored disbelief that his brother couldn't sense it. "This hasn't happened in almost 5,000 years! I just thought maybe you should go check on your little Asgardian friends. You know, the ones that have stories about you and stuff? If you do go, say hi to Loki for me. I love that kiddo!" Gabriel disappeared, leaving Castiel to ponder his words.

The next moment he was in the healing chambers of Asgard, watching as a human was looked over by their healers. Thor was the first to spot him and waved him forward.

"Castiel! What brings you here? Loki is still imprisoned," the thunder god boomed. The others in the room glanced over, questioning who the stranger was, but didn't say anything. If he was with Thor then obviously he was safe. Castiel drifted off, instead focusing his attention on the human. Her soul was pulsing in a way he hadn't seen in almost 5,000 years . . .

"No," he whispered before disappearing to the hiding place of the Aether. All was silent; the force of darkness was missing.

The sheer horror of the situation dawned on him. Castiel's mind flashed back to the war. Images of people dying bloody and being sucked up into miniature black holes, bones cracking and shattering filled his brain, causing him to give a gasp of terror.

In a moment, Castiel was right next to Thor. "The Aether! How did she get it!?"

Thor jolted, taking a step back. "The Aether? But that was destroyed thousands of years ago! What has stemmed this outburst?"

Just then, Odin walked in, looking quite displeased. "My words are mere noises to you that you ignore them completely?"

Thor took his attention off of Castiel and instead directed his gaze at his father. "She's ill."

"She is mortal. Illness is their defining trait." Odin didn't seem to notice the startled angel-who was quite smaller than most Asgardians in the room-standing behind Thor.

"I brought her here so we can help her."

"She does not belong here in Asgard any more than a goat belongs at a banquet table."

Jane sat up, just turning away from talking about the 'Soul Forge.' "Did he just-" She looked at Thor in disbelief. "Who do you think you are?" She glared at Odin.

Looking at her in disdain, he replied firmly,"I am Odin. King of Asgard. Protector of the Nine Realms."

Jane hesitated. "Oh, well, I'm . . ."

"I know who you are." He glanced about idly. "But I do _not_ know who this is!" Kind Odin said suddenly, his attention now on the angel in the room. Castiel looked up, his gaze as stony and same as ever. "Name yourself or you shall be killed!" The King's guards surrounded the seemingly defenseless warrior.

"Father, this is Castiel. He is an ally," Thor said, putting a hand out towards the said man that was currently staring nonchalantly at the spears directed at him.

"Why did you bring him?"

"I didn't. He came here of his . . . own accord."

Castiel ignored the guards and faced Odin. "The Aether is missing. And it's in"-the angel pointed fiercely at Jane-"her veins, pumping through her. I don't know how she got it, but it must be returned to its place."

Odin looked down at the human female laying under the Soul Forge. Quickly going around to her arm, he placed his large hand just over her skin. Red light flickered and shone like sunlight reflecting off the ocean showed through.

"It's impossible."

"Not as impossible as once thought, it seems," Castiel said gravely. Odin turned around swiftly. He began a brisk gait down the halls.

"Come with me."

Odin led them down the hallways toward the Hall of Science. The tree of Yggdrasil sat at the center of the room, but they continued into the library wing. There on a table was a thick book, enhanced with magical properties. The King opened it.

"There are relics that predate the universe itself. What lies within her appears to be one of them. The Nine Realms are not eternal. They had a dawn, as they will have a dusk. But before that dawn the dark forces, the Dark Elves, reigned absolute and unchallenged," Odin began.

Castiel narrowed his eyes. "We should skip the obviously long story telling. Getting the Aether out of her body is the priority."

Odin glared at the haughty angel with a look that would have normal Aesir down on their knees. "And who are you to question my authority?"

"Who cares if this simple human understands what is inside of her? We must destroy the Aether."

"Simple? You are messing with the wrong-" Jane's quickly approaching slap was halted as Castiel flung a hand back, his bright blue gaze still on the King. The woman held back a gasp, settling for a sharp exhale through her nose and her eyes widening.

"There is no way to extract it without killing us. Even I cannot do it," Odin murmured.

Thor tilted his head at Castiel. "Surely you can do it? You've done so much."

Castiel sighed, his shoulders drooping just a bit. "The Aether transforms matter into dark matter. My Grace, in its entirety, is pure soul. If it were to be touched, just barely, it would destroy my being. I don't know how much, but I'd rather not take any chances."

"I see. So there is no way we can extract the Aether from Jane?"

Castiel shook his head. "No."

* * *

Castiel sat on a wall, high above Asgard. His feet dangled beneath him, the distant Aesir below looking like ants. A slight wind blew the angel's overcoat array, the straps that would've held it to his body flapping. Two dark blue eyes stared out at the emptiness.

"Castiel."

"I am aware of your concerns," Castiel regarded levelly to the golden warrior standing next to him.

"I believe you should tell the Allfather who you actually are," Thor said. He dropped down to Castiel's level. His cape billowed out behind him.

"Why am I to care who he thinks I am?"

"You are an angel; surely he's heard of you and your kind."

Castiel sighed loudly, earning a questioning look from Thor.

"What's ailing you?" the thunder god asked.

"You may think me just an angel, but do you actually know the legend of the battle between your people and the Dark Elves?" Castiel asked softly.

"Of course I do. Every Aesir does."

"Tell me it." He paused. "Quickly."

Slightly puzzled, Thor gave him a quizzical look but complied. "Well, the Dark Elves wanted to bring eternal night, but we stopped him. King Bor led a legion against Malekith with the help of a warrior. Malekith sacrificed his own kind in the process to defeat our army, and after that, King Bor destroyed the Aether afterwards. Well, supposedly. It's hard to think that now after what happened."

The angel nodded. "Describe the warrior."

"Describe? Surely this is a jest."

"I know your books have some sorts of descriptions," Castiel urged, "now tell me."

Thor exhaled through his nose, thinking. "I heard that the warrior had the heart of a soldier. He was completely battle trained, even though the Asgardians hadn't trained him."

"Go on."

"He had the deepest blue eyes, some said."

"Good. Continue."

"This last part was the oddest, but in a book about the war, there was a report that he was as fast as light. They'd see him one place and then the next moment, he'd have slain ten elves somewhere else-"

Thor stopped talking, his mouth having fell open as the gears clicked together in his mind. Castiel met his gaze briefly before turning away.

"You"-Thor jumped to his feet-"You're the great warrior!"

Castiel stayed where he was. He didn't look up at Thor, just stared into the distance. "Yes."

"Why didn't you say anything?"

"Why would I want to?" Castiel whispered. His gaze fell and Thor's shock changed to worry. "The war was horrible; there was much blood and violence. The devices the Dark Elves had to kill with were demonic. I fought with your kind so the universe would not die. I never said I enjoyed it."

"I am sorry. I didn't know you felt this way."

"Of course you wouldn't. You didn't even know." The angel continued staring at the faraway horizon.

"You should still tell the Allfather. Then he would listen to you! He would trust your advice."

"Maybe so. But I'd rather go without his."

"Why? He knows more than you give him credit for." Thor gave the smaller man a stern glare, which was promptly ignored.

"I don't doubt his knowledge." He paused. "It is his ideals that worry me. He does not know what is going to happen."

"My father does indeed understand the graveness of this situation!"

"Are you so sure? One does not always know what is best," Castiel responded levelly.

"And you are saying you do?" Thor snapped.

"Possibly. But never assume."

"I do not _assume_, I know!"

Castiel snapped his deep blue gaze up to the Asgardian. "Are you actually saying you know?"

"Yes- wait, why hasn't anyone else mentioned your wings? If they'd seen them, surely they'd know who who you are," Thor pointed out, his eyes narrowing.

"I hid myself. They know not what or who I am. Best it stays that way," Castiel answered absentmindedly with a wave of his hand.

"You've got to be the most stubborn extraterrestrial being I've ever had the pleasure of meeting."

"I very much doubt it."

Thor raised an eyebrow. "The part about meeting you was true. The stubborn part- mostly true. You have your own code and your own rules. You're barely part of this world."

"I'm not. So you are correct." The angel held no amount of mirth in his voice.

"Serious."

"Of course."

Thor watched Castiel for a few more moments. The angel seemed pensive, his hands together and eyes scanning the beautiful Asgardian horizon.

"I shall go for now. Jane is most likely searching for me. I have been gone longer than I intended," Thor said. Castiel nodded silently. He didn't meet the god's eyes nor did he turn his face away from the golden sky. Thor stood quietly, then finally turned away. He leapt from the pinnacle.

* * *

**Alright, first chapter done. Buckle your seat belts, it's gonna be a bumpy ride.**


	2. Frigga

Castiel carefully scanned the horizon. There was no sign of any disturbances. At least, not yet. Castiel pondered his position. The Aether was unable to be extracted from the female's veins- Jane, her name was. Thor seemed to have an interest in her. Castiel had not meant to insult her earlier, but he'd been frantic to get the Aether out of her and return it to its place- neither of which they could do. So they were stuck.

_Perhaps we can devise some sort of plan . . . Maybe-_

Sirens wailed from down in the palace. Castiel's eyes directed downwards, his gaze icy. In an instant, he was flying next to Thor as a celestial wavelength, unknown to him. Thor touched down, and Castiel appeared next to him. The thunder god didn't notice him at first. He glanced at the sky for a brief moment, saw Castiel, looked back at the sky, and did a quick double-take when he realized the angel was standing there.

"Castiel!" Thor boomed heartily. "I should have known you'd come to help. The dungeon's alarms are going off." The god tightened his grip on his hammer, then stormed towards the dungeons. Castiel followed him casually. Once near the doors, the sound of fighting increased. More soldiers poured from the castle, faces stoic. Thor smashed the doors open, growling. Castiel was nearly shoved by the group of Asgardian soldiers flooding the dungeon area. Around them, a dozen more fighters battled against the Marauders who were escaping their cells. Upon seeing Thor, they hesitated.

"Return to your cells and no further harm will come to you. You have my word," Thor said calmly. A wild fist hit him in the face. Thor grabbed the Marauder who did it. "Very well, you do not have my word." He tossed the man aside with a smash from his own fist. Thor looked back at his partner and nodded to the chaos. Castiel glanced around, perplexed, but Thor dashed off. Taking that as his cue to help end this madness, the angel twisted around to stop an incoming Marauder. The prisoner screamed as the angel blade was forced through his armor. Castiel let the man drop to the floor. He weaved his way around idly, fighting with whatever prisoner dared enter his path. That was when a strange rumble shook the palace walls. Thor, his friends, and Castiel glanced around, puzzled. Thor cast his gaze over to Loki, who returned it with a somewhat uneasy smirk.

"Come. We must go," Thor commanded. The fighting was over. "Something is happening." 

* * *

"Castiel! Go help defeat the elves. They've invaded the castle," Thor ordered, sprinting towards their chambers.

"I sense an evil presence," Castiel responded, barely keeping pace with the god of thunder. "Be wary."

"Of course there's an evil presence! Now GO!"

Castiel stopped as he was shouted at. Thor was very stressed about this. But Castiel could feel something . . . and it was where Thor was headed. Taking off, the angel flew into the room, startling the beings inside. Castiel felt his vessel's heart beat louder.

Malekith.

The elf's eyes flashed with recognition. Malekith stood taller, lifting his chin to face Castiel.

"Well, well, well," Malekith started, "what have we here?" He began to circle the angel.

"Let her go, Malekith," Castiel commanded, eyes dark. Their gaze briefly flitted over to Frigga, who was being held by Kurse.

"I feel like we've met before." The elf's tone was mocking. He pretended to think about it as he paced. "Oh yes, I remember. Your race, the warriors of Heaven." Malekith used the word scornfully.

"Be wary of your tone."

"Oh yes," Malekith snarled. "I know who you are, warrior."

Castiel allowed his angel blade to fall from his sleeve. "I know who you are as well. And I order you to let the woman go."

Malekith glanced at the blade in Castiel's hand and then back at Kurse. As he directed his attention back to Castiel, a wicked smirk spread across his face.

"I don't think I will."

There was a sharp gasp from Frigga as Kurse slid the blade into her side. It was not even all the way into her when Castiel was beside her, angel blade being forced into Kurse. He dropped her and swung around as the silver blade was stopped by his armor. A giant hand came up and slammed down on Castiel, who jumped away. The two began to fight.

A bolt of lightning zapped through the room. Malekith- faintly seen out of the corner of Castiel's eye as he tussled with Kurse- went down, falling onto the short flight of steps to the balcony. A cry of anguish ripped through the air as Thor flew into the room. Castiel briefly turned his face towards the action and regretted that instantly as Kurse punched him in the chest. Castiel went soaring across the room . . . and straight off the balcony. Kurse, once clear of his fight, ran towards the felled Malekith and leapt off the balcony, straight onto a passing ship. They were gone before Thor could even grab Mjolnir. 

* * *

Thor's heart was filled with grief. He sat in Frigga's chamber, eyes staring at the blood stain on the carpet. Her body and Odin were long gone, but he had stayed.

He had failed.

A fist clenched, tears welling up in his eyes, and the next thing he knew, there was a hole in the wall. Thor weakly looked around as he felt the tears dripping down his face. He pushed up from one knee. There was something missing here . . . oh yeah. With his mother's death and the escape of Malekith, he'd forgotten all about the figure he'd seen falling out of the sky just a moment before that.

Thor picked grabbed Mjolnir up from the floor, grateful for the familiar weight in his hand. He casually strode towards the balcony, eyes roaming downwards. In a single, swift moment, Thor hopped over the balcony. Upon reaching the ground, he glanced about. Finding what he was searching for, the thunder god padded over.

"Castiel, you have seen better days, my fine feathered friend," Thor said in a bitter yet somewhat amused tone. "Here, allow me to assist you." He reached down and took hold of the angel by the arm, hauling him to his feet. Castiel shook his head, eyes distant.

"That was . . . most unpleasant," he murmured, stumbling a few steps. Thor allowed his eyes to scan Castiel, but he didn't find any injuries.

"You are well, yes?"

"Of course." The angel nodded in response. He watched Thor for a short moment.

"Good." Thor began to walk away. "Walk with me." Castiel paused, hesitant, but followed after a moment. The streets of Asgard were empty, many inside their houses mourning for lost loved ones. Castiel glanced about, a dreadful sense of foreboding falling over him. He raised an eyebrow at Thor as they proceeded to go into a more protected side street near the castle. Thor wasn't saying a word yet. But suddenly he pulled Castiel to the side, grabbing his arm, nearly pushing him into the wall.

"Now, tell me: what can you do with healing others?"

Castiel searched Thor's determined expression. "Is this about . . ." He tried to think of a name to place with her but couldn't. Thor waited for him to complete his phrase, but when he didn't, he finished for him.

"My mother: Frigga," Thor admitted, eyes shining with grief. "She was killed by that beast."

"Kurse." Castiel removed Thor's arm from his, easily doing so. "And I'm sorry."

"You're _sorry?"_ Thor's demeanor changed. "You were in there! Why didn't you save her?!"

"I tried!"

Thor smashed his forearm into Castiel's chest, pushing him against the wall and pinning him there. "You are no sort of warrior if you cannot even save a life!" He paused, trying to control his anger. Castiel once again grabbed Thor's arm and removed it from his form.

"I cannot save everyone."

Thor focused him with a watery glare that quickly turned into a look of anguish. "Can- can you save her?"

Castiel hesitated. 

* * *

"I know not what you are doing, but will you please put me down?"

Thor was swinging Castiel around in a circle, the angel hugged to his broad chest. A smile of relief was plastered on his face, tears of joy springing up in his eyes. Suddenly, Thor set him back on the floor, looking down upon him.

"Come! We must go!" the god of thunder declared happily. Thor dashed off, startling Castiel, who quickly followed on wing. The thunder god romped down the golden hallways, navigating the twists and turns of the castle. Soon, they came about the "morgue" of the palace. Castiel reappeared as Thor burst in, surprising the guards who were standing outside. The various Aesir inside- healers and maids- glanced up, stopping at the intrusion.

"Castiel, come forward," Thor proclaimed. The angel shuffled around the thunder god. The Asgardians looked puzzled. Frigga's inanimate body lay still on the table as she was prepped for the Ceremony of Death. "I ask you all to back away, please."

"With all due respect, you cannot be in here," said Eir, the head of the healers.

"Just let my friend through. I promise, nothing but good will come from this."

"Thor-"

The god silenced her with a wave of his hand. Eir scoffed as she was nudged to the side, allowing Castiel to make his way to Thor's mother's pale form.

"You cannot allow that stranger to touch the Queen's body!" Eir barked.

"Just be quiet, please. I mean you no disrespect," Thor apologized.

"Me?! I'll get the guards if I have to!"

"Shush, woman!" Thor exclaimed as Castiel moved forward to place a hand upon Frigga's forehead. The room fell silent in less than a second. Castiel gently brushed a hand across her head and then allowed his arm to fall back down at his side. The room remained silent.

It was then that Frigga began to shift. Her eyes fluttered open, mouth open to pull in a breath. Thor nearly jumped with delight, quickly approaching his mother. Frigga sat up, her strength returning. She saw her son and allowed him to help her stand.

"How- how did-" Eir stammered, voicing aloud nearly the whole room's thoughts.

"Thor? What . . . How? I . . . I died," Frigga stammered, hand feeling up and down her back where she'd been stabbed. Thor gently took ahold of her hands, smiling at her.

"Aye, it is but in the past. You are well now, and that is all that matters," Thor reassured.

Frigga blinked at her son for a moment before embracing him in a tight hug, tears in her eyes. Thor returned it with gusto. After a few moments of bonding, they released their hold.

"We must go and tell Odin. He will be more than pleased to see you," Thor continued. "Castiel, I-" As he turned around, the thunder prince discovered that Castiel was no longer present. 

* * *

Thor found the angel on the balcony of some random uninhabited room in the castle. Castiel gazed out over the shining city of Asgard.

"Castiel-"

"Do not speak to me," Castiel ordered, voice angry. Thor blinked in astonishment; was he talking to him?! But then again . . . who else could it have been? The angel's back was ramrod straight, hands at his sides. Thor hesitantly walked forward, face full of confusion.

"Friend, what is the matter?"

"You know not what you have caused."

"Me?!"

Castiel whirled around, blue eyes full of fire. "Frigga's death was not supposed to happen. That is the only reason I agreed to revive her. But now, because of that, the whole future is changed."

Thor fumbled briefly for a moment. "Do not just blame me! As you said, you agreed to heal her! If her death was not meant, then how could that possibly change the future? You are being foolish."

Castiel glared. "Foolish? Think of you are speaking to."

* * *

**Frigga's too awesome to die; your argument is invalid.** **I hope you guys enjoy it so far . . . it's a little weirder than the first "Castiel the Avenger", but it should be as good in the end. **


End file.
